In recent years, active studies have been conducted on SON (Self Organizing Network), which autonomously optimizes radio parameters and network configurations in wireless communication systems such as cellular systems, in view of operation cost (OPEX) reduction and the like. Standardization of SON functions is under way also in LTE (Long Term Evolution) of 3GPP (3rd Generation Partnership Project). In order to implement Optimization of load balancing (Mobility Load Balancing: MLB) among the Self-Optimization functions included in SON, various methods for acquiring load information have been proposed.
For example, according to a method disclosed in PTL 1, in a system in which a plurality of network operators share a base station, the base station monitors a load ratio attributable to each operator and notifies the monitoring results to another base station over the X2 interface by using a Resource Status Request/Report message or the like. Base stations exchange load information per operator (per PLMN (Public Land Mobile Network)) in this manner, thereby attempting to accomplish load balancing.